Has any guidance been reported regarding Ibn Kathir and Abu Amr al-Basri's recitation of the word {سُدًّا} (suddan) in Surat Ya-Sin with a dammah on the sin, and with a fathah in Surat al-Kahf, or does that stem from following the روایت (transmission)?

Following the narration (riwayah) is the basis for the variations in recitations (qira'at). There is a difference in explaining the meaning of "al-sadd" (السد with fathah) and "al-sudd" (السُّد with dammah). Some say they are two different linguistic forms (lughataan). Others say that the word with dammah is a noun (ism) and the word with fathah is a verbal noun/infinitive (masdar). Still others say that the word with dammah refers to what is created by Allah, and the word with fathah refers to what is done by humans. However, this last opinion has been refuted by the existence of recitations with both dammah and fathah in different contexts, such as the barrier of Dhul-Qarnayn and the barrier in Surah Yasin, which indicates that they are indeed two different linguistic forms.